האוניברסיטה העברית בירושלים THE HEBREW UNIVERSITY OF JERUSALEM EFFECT OF NEST-SITE MICROCLIMATIC CONDITIONS ON NESTING SUCCESS IN THE LESSER KESTREL (FALCO NAUMANNI) By ORLI BOBEK, ADIV GAL, DAVID SALTZ AND UZI MOTRO Discussion Paper # 721 (July 2018) מרכז פדרמן לחקר הרציונליות THE FEDERMANN CENTER FOR THE STUDY OF RATIONALITY Feldman Building, Edmond J. Safra Campus, Jerusalem 91904, Israel PHONE: [972]-2-6584135 FAX: [972]-2-6513681 E-MAIL: [email protected] URL: http://www.ratio.huji.ac.il/ Effect of nest-site microclimatic conditions on nesting success in the Lesser Kestrel (Falco naumanni) Orli Bobek Department of Ecology, Evolution and Behavior, The Hebrew University of Jerusalem, Jerusalem 91904, Israel Adiv Gal Department of Ecology, Evolution and Behavior, The Hebrew University of Jerusalem, Jerusalem 91904, Israel David Saltz Mitrani Department of Desert Ecology, Blaustein Institute for Desert Research, Ben Gurion University of the Negev, Sde Boker Campus 84990, Israel Uzi Motro1 Department of Ecology, Evolution and Behavior, Department of Statistics, and The Federmann Center for the Study of Rationality, The Hebrew University of Jerusalem, Jerusalem 91904, Israel 1 Corresponding author. Email address: [email protected] Key Words: Lesser Kestrel, Falco naumanni, Nest Microclimate, Nesting Success, Nest-site Selection, Nesting Boxes. 2 ABSTRACT Capsule: Microclimatic conditions in the nest of the Lesser Kestrel (Falco naumanni), particularly the percentage of time of extremely low humidity, affect breeding success. Aim: (1) To study the effect of within-nest temperature and humidity on nest productivity, and the correlation between nest productivity and the order of dates on which nests were occupied by the parents. (2) To compare microclimatic conditions in the nest, breeding success and order of occupation between nests under tile roofs and artificial nest boxes. Methods: Three different Lesser Kestrel colonies in Israel – one rural, one urban and one in an open country habitat. Data loggers, that measure temperature and humidity, were put in 39 nests for the entire breeding period. The number of fledglings was recorded for each nest, as well as the date of occupation. Results: (1) Full microclimatic data from 35 nests suggest that percentage of time of extremely low humidity is the major predictor of nest productivity. (2) The urban colony had the lowest breeding success of the three colonies. (3) Sites of more successful nests were occupied earlier. (4) No significant difference in mean productivity between nests in roofs and nest boxes, but nests in roofs were occupied earlier. Conclusion: Nest microclimate affects nesting success in addition to colony location. 3 Habitat selection in birds of prey is influenced by climatic conditions, the availability of appropriate prey, the presence of competitors and (in some species) the presence of predators, and the availability of suitable nesting sites (Janes 1985). The optimal characteristics of a high-quality nest-site are species specific, and can sometimes be deduced either by observing the rate of success of different nests or by the choice made by the birds themselves (McClaren et al. 2002). Cliff and cavity nesters (such as most Falco species) are among the groups that are clearly limited by the availability of nesting places (Newton 1979). Due to limitation of nesting places, some falcon species have adapted to nest in association with human dwellings – rural as well as urban – e.g. the Peregrine Falcon (Falco peregrinus), the American Kestrel (Falco sparverius), the Eurasian Kestrel (Falco tinnunculus) or the Lesser Kestrel (Falco naumanni). The Lesser Kestrel is a small falcon that breeds colonially and nests mainly in small cavities – on cliffs, on walls of abandoned quarries, under tiled roofs of rural and urban buildings, in barns and stables, or in old castles and churches (Cramp and Simmons 1980). It is a migrating species, breeding mainly in the Mediterranean, the Balkans and Anatolia, and in western and central Asia. It winters mostly in sub- Saharan Africa, but also a small number of adults winter in the southern part of the breeding range from the Iberian Peninsula to Turkey, Azerbaijan, India, Myanmar, and southern China. The European and Asian breeding population and the wintering numbers in South Africa suffered a rapid decline from 1950, and the species was declared as Vulnerable by the IUCN. Recent evidence, however, indicates a stable or slightly positive population trend overall during the last decade. Consequently, it was downlisted from Vulnerable and now qualifies as Least Concern (IUCN 2018). The main cause for the past decline of the lesser kestrel population in its Palearctic 4 breeding grounds has been habitat degradation, primarily because of agricultural intensification and the associated land use changes and the use of pesticides. Another cause is the loss of suitable breeding sites – the abandonment and collapse of old rural buildings on one hand, and restoration works of rural and urban buildings on the other hand (Iñigo & Barov 2011). Artificial nest boxes are used in order to augment the declining population, especially in Europe (Pomarol 1996, Catry et al. 2007, Bux et al. 2008) and in Israel (Liven-Schulman et al. 2004). Nest site characteristics and their correlation with breeding success and the frequency of use of the site have been studied for many raptor species and populations. These characteristics are usually the nest type and substrate, its location, orientation and the within nest microclimate conditions. With reference to falcons, studies have been conducted both on natural and artificial nests. Studying natural nests, Raphael (1985) reports that orientation influences nest preference by American Kestrels, probably due to thermoregulation advantages. Studying the use of artificial nest boxes by this species also show a preference to particular orientations (Rohrbaugh & Yahner 1997, Butler et al. 2009). Examining nest boxes of Eurasian Kestrel in Finland, having different size and orientation, Valkama and Korpimäki (1999) found a preference to certain orientations and to intermediate nest size. Comparing the use of natural nests vs. nest boxes by Eurasian Kestrels in central Spain, Fargallo et al. (2001) found less predation and larger productivity in nest boxes, but with increased level of infestation by parasites. Negro and Hiraldo (1993) studied nest site occupancy and success by Lesser Kestrels in three colonies located in churches in southern Spain. Nests sites which were located high above the ground were selected by the breeders more frequently and earlier than available sites which were lower on the walls – probably to avoid 5 predation and disturbance by predators and humans. Higher nests also realized a higher breeding success. A similar preference of Lesser Kestrel to higher nests was found in Sicily (Sarà et al. 2012). Comparing artificial and natural nests of Lesser Kestrel in Italy, Bux et al. (2008) showed a similar breeding success in nest boxes as in attic nests, but smaller than in natural cavities. Nest boxes installed in Portugal helped in increasing the Lesser Kestrel population (Catry et al. 2007). Moreover, the kestrels actually preferred the artificial to the natural nest sites. A study of Lesser Kestrel population in Sicily by Di Maggio et al. (2013) demonstrated that nest type (holes vs. nests under roof tiles) and orientation affect the microclimate within the nest, and consequently the hatching and fledging success. Liven-Schulman et al. (2004) conducted observations on Lesser Kestrels in three different breeding areas in Israel: a rural colony in the Alona district, an urban colony in the city of Jerusalem and a cliff colony in the Judean desert (open-landscape colony) about 10 km east of Jerusalem. They found a significantly smaller mean fledgling rate in Jerusalem, compared to the Judean desert and to Alona. They attributed this differential success mainly to lower feeding rates in Jerusalem. The loss of hunting grounds as a result of the rapid pace of development of the city forced the adults either to hunt in sites more than 10 km east of Jerusalem or in the city parks and lawns, where the use of pesticides (mainly Diazinon) against mole-crickets (Gryllotalpa gryllotalpa) affects kestrels activity. In the present work we tried to learn if factors other food limitation, such as microclimate within the Lesser Kestrel nests, have an effect on the nesting success in Israeli colonies. Methods 6 The Lesser Kestrel in Israel The Lesser Kestrel is a summer visitor in Israel, arriving during the second half of February, and nesting usually terminates in early June. They breed in colonies, both adjacent to human settlements (rural and urban) and in the open country, where they are found usually on cliffs. Clutch size is between 3 to 6 eggs (Cramp & Simmons 1980). The estimated breeding population in Israel is 364 pairs – 63% in rural settlements, 5% in urban and 32% in the open country, mostly in quarries (Perlman 2013). They feed almost exclusively on arthropods, mainly of the Coleoptera, Orthoptera and Solifugae orders, but also on reptiles and rodents (Gal 2006, Kopij & Liven-Schulman 2012). Study Area Observations were carried out in three colonies, each in a different area and representing different environmental conditions: (1) In Moshav Amikam, within the Alona Regional Council (32°34’N 35°01’E, 100m asl), representing a rural colony. (2) In the city of Jerusalem (31°47’N 35°13’E, 800m asl), representing an urban colony. (3) On a cliff in the Revaya quarry, on the lower slopes of Mt. Gilboa (32°27’N 35°27’E, 120m asl), representing an open country colony. Field Sampling In each colony, data loggers (MicroLog Temp/Hum, Fourier Systems Ltd.), that recorded temperature and humidity every hour, were placed in several nests for the entire nesting period. The sensors were positioned inside the nest cavity, about 10 cm from the clutch. Loggers and data were retrieved only at the end of breeding season.